Robert , Louisiana -LRB- CNN -RRB- -- Three attempts to pump mud and 16 tries to stuff solid material into a breached Gulf of Mexico oil well failed to stop the flow , top BP executives said Saturday , and engineers and executives with the oil giant have decided to `` move on to the next option . ''

That option : Place a custom-built cap to fit over the `` lower marine riser package , '' BP chief operation officer Doug Suttles said . BP crews were already at work Saturday to ready the materials for that option , he said .

Suttles said three separate pumping efforts and 30,000 barrels of mud -- along with what chief executive officer Tony Hayward described as `` 16 different bridging material shots '' -- just did n't do the trick .

`` We have not been able to stop the flow , '' a somber Suttles told reporters . '' ... Repeated pumping , we do n't believe , will achieve success , so we will move on to the next option . ''

Suttles and other officials said that the `` top kill '' attempt to stop the flow did so -- but only as long as they were pumping . When the pumping stopped , the oil resumed its escape . And Coast Guard Rear Adm. Mary Landry said that BP would resume using undersea dispersants for the new attempt to trap the oil .

Suttles said the lower marine riser package cap `` should be able to capture most of the oil '' that has fed what is now the largest oil spill in U.S. history , but he cautioned that the new cap will not provide a `` tight mechanical seal . ''

`` We 're confident the job will work , but obviously we can not guarantee success at this time , '' he said .

Engineers should be ready in about four to seven days to make the fresh attempt , he said . Landry said officials were `` disappointed in today 's announcement , '' but noted that the immediate efforts to stop the flow were never intended to be permanent .

`` The real solution , the end state , is a relief well , '' she said . BP currently is working on two relief wells , but they are not expected to be ready until August , Suttles said .

Earlier , Suttles said that BP engineers would try to place a second blowout preventer -- the piece of equipment that failed when the Deepwater Horizon exploded on April 20 -- should the lower marine riser package fail . The failed blowout preventer is a 48-foot-tall , 450-ton apparatus that sits atop the well 5,000 feet underwater .

Suttles and Landry praised the clean-up efforts , however , in light of the failure of the `` top kill '' attempt to stop the flow .

`` It 's a tribute to everybody that we only have 107 miles of shoreline oiled and only 32 acres of marsh , '' Landry said .

Meanwhile , teams in Louisiana were working Saturday on a clean-up project aimed at protecting coastal marshes . Plaquemines Parish President Billy Nungesser has said that machines would suck oil out of marshes Saturday after crews determined where to deploy them .

But Nungesser told CNN that BP needed to `` step up to the plate tonight to save our wetlands '' by using its might to create sand barriers to prevent the oil from moving into the marshes .

`` BP needs to say it will pay to move those dredges and pump that sand berm , '' he said . `` We are gon na die a slow death if we do n't get that berm . We 've got to have that barrier island . ''

President Barack Obama , who toured the area Friday , said federal officials were prepared to authorize moving forward with `` a portion of '' an idea proposed by local officials , who want the Army Corps of Engineers to build a `` sand boom '' offshore to keep the water from getting into the fragile marshlands .

But Nungesser said the marshes could n't wait and that the effort needed to start immediately to save the Louisiana wetlands .

Government scientists on Thursday said as many as 19,000 barrels -LRB- 798,000 gallons -RRB- of oil were spewing into the ocean every day , making this disaster perhaps twice the size of the Exxon Valdez incident .

Previously , BP officials and government scientists had said 5,000 barrels -LRB- 210,000 gallons -RRB- of crude were flowing out daily .

`` This is clearly an environmental catastrophe , '' Hayward said Friday . `` There 's no two ways about it . ''

In an e-mail message sent out after the announcement Saturday , Hayward said he was `` disappointed that this operation did n't work . ''

`` The team executed the operation perfectly , and the technology worked without a single hitch , '' he said . `` We remain committed to doing everything we can to make this situation right . ''

Obama 's visit to the region came under intense political pressure to take control of the situation .

`` We want to stop the leak , we want to contain and clean up the oil and we want to help the people in this region return to their lives and livelihoods as soon as possible , '' the president told reporters .

About 25 percent of the Gulf of Mexico exclusive economic zone has been put off limits , according to the National Oceanic and Atmospheric Administration , and fishermen are worried the gushing oil will take a more serious toll than Hurricane Katrina did in 2005 .

`` Katrina was nothing but rain , water and wind . This is poison . It 's gas , '' oysterman Arthur Etienne said .

CNN 's Anderson Cooper contributed to this report .

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NEW : BP will try lower marine riser package cap next

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NEW : Lower marine riser package cap will capture most , but not all of oil flow

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NEW : Officials : Only sure option is relief wells , still 2 months away

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NEW : Parish president wants BP to build sand barrier islands now

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Workers toil on beaches and in marshes to clean up